The rm utility attempts to remove the
non-directory type files specified on the command line. If the permissions of
the file do not permit writing, and the standard input device is a terminal,
the user is prompted (on the standard error output) for confirmation.

Attempt to remove the files without prompting for confirmation, regardless
of the file's permissions. If the file does not exist, do not display a
diagnostic message or modify the exit status to reflect an error. The
-f option overrides any previous
-i options.

Request confirmation before attempting to remove each file, regardless of
the file's permissions, or whether or not the standard input device is a
terminal. The -i option overrides any
previous -f options.

Request confirmation once if more than three files are being removed or if
a directory is being recursively removed. This is a far less intrusive
option than -i yet provides almost the
same level of protection against mistakes.

Overwrite regular files before deleting them. Files are overwritten three
times, first with the byte pattern 0xff, then 0x00, and then 0xff again,
before they are deleted. Files with multiple links will not be overwritten
nor deleted and a warning will be issued. If the
-f option is specified, files with
multiple links will also be overwritten and deleted. No warning will be
issued.

Specifying this flag for a read only file will cause
rm to generate an error message and
exit. The file will not be removed or overwritten.

Attempt to remove the file hierarchy rooted in each
file argument. The
-R option implies the
-d option. If the
-i option is specified, the user is
prompted for confirmation before each directory's contents are processed
(as well as before the attempt is made to remove the directory). If the
user does not respond affirmatively, the file hierarchy rooted in that
directory is skipped.

The rm utility removes symbolic links, not
the files referenced by the links.

It is an error to attempt to remove the files
/, . or
...

When the utility is called as unlink, only
one argument, which must not be a directory, may be supplied. No options may
be supplied in this simple mode of operation, which performs an
unlink(2)
operation on the passed argument. However, the usual option-end delimiter,
--, may optionally precede the argument.

The rm utility exits 0 if all of the named
files or file hierarchies were removed, or if the
-f option was specified and all of the
existing files or file hierarchies were removed. If an error occurs,
rm exits with a value >0.

The rm command uses
getopt(3)
to parse its arguments, which allows it to accept the
‘--’ option which will cause it to stop
processing flag options at that point. This will allow the removal of file
names that begin with a dash (‘-’). For example:

rm -- -filename

The same behavior can be obtained by using an absolute or relative path
reference. For example:

rm /home/user/-filename

rm ./-filename

When -P is specified with
-f the file will be overwritten and removed
even if it has hard links.

The rm utility differs from historical
implementations in that the -f option only
masks attempts to remove non-existent files instead of masking a large variety
of errors. The -v option is non-standard
and its use in scripts is not recommended.

The -P option assumes that the underlying
storage overwrites file blocks when data is written to an existing offset.
Several factors including the file system and its backing store could defeat
this assumption. This includes, but is not limited to file systems that use a
Copy-On-Write strategy (e.g. ZFS or UFS when snapshots are being used), Flash
media that are using a wear leveling algorithm, or when the backing datastore
does journaling, etc. In addition, only regular files are overwritten, other
types of files are not.